AT&T has launched their third generation wireless service today. UMTS will initially be available in San Francisco, Seattle, Phoenix, and Detroit.
In order to use a UMTS phone, you must be on a GSM America plan, or one of two eligible Flat Rate plans (for those interested in using it as a data device).
In addition, when purchasing a UMTS phone, you are required to change data plans. The only data plan available is the $24.99 Unlimited mMode plan, also launched today. This data plan allows for unlimited handset-usage. AT&T does state that any tethered usage will be billed at $.001/KB, and that rate also applies when the SIM card is removed from a UMTS phone and inserted in any other device.